"Most previous studies of risk, such as toxin exposure or social maltreatment, have thrown males and females or young and old people together in ways that fail to recognize age-, sex- and trait-specific vulnerabilities," says David Geary. "If we don't measure the right trait or measure it at the wrong time or in the wrong sex, we'll miss many negative consequences of risk exposure." (Credit: Jocelyn Kinghorn/Flickr)

evolution

Add ages and sexes to locate health risks

A new book offers a way to identify when specific traits—like height or language ability—are more vulnerable in either of the sexes or at particular ages.

Historically, males have been considered the vulnerable sex, sometimes called “male vulnerability.” Charles Darwin noted that boys are more likely to die in infancy than girls and have a higher risk of premature death throughout their lifetimes.

David Geary, professor of psychological sciences at the University of Missouri, now suggests that research in “male vulnerability” should be expanded to include “female vulnerability.”

Using evolutionary theory and basic biological principles, he proposes a method for identifying when specific traits, such as height or language abilities, are more easily compromised in one sex or the other or at some ages but not others.

Identification of age-, sex-, and trait-specific sensitivities will enable a more comprehensive assessment of how disease, poor nutrition, social abuse, and environmental toxins undermine human wellbeing.

The right time, the right sex

“If we want to fully understand risks to people, then we have to understand the traits that are most likely to be compromised by these risks, the ages at which stressors are most likely to compromise them, and the different ways in which boys and girls and men and women can be affected,” says Geary.

“Most previous studies of risk, such as toxin exposure or social maltreatment, have thrown males and females or young and old people together in ways that fail to recognize age-, sex-, and trait-specific vulnerabilities.

“If we don’t measure the right trait or measure it at the wrong time or in the wrong sex, we’ll miss many negative consequences of risk exposure. The method I’m proposing will allow researchers to identify these very specific risks ahead of time and ultimately prevent or ameliorate their expression.”

From animals to people

To evaluate the method, Geary reviewed thousands of studies across 125 species of birds, fish, insects, and mammals, documenting age- and sex-specific vulnerabilities in key traits.

The specific vulnerabilities can vary across species and sex, but are tied together with a simple concept: the development and expression of traits that have been elaborated over evolutionary time are easily disrupted by exposure to environmental and social stressors.

Geary applied the same concept to people identifying age- and sex-specific vulnerabilities including physical traits, such as pelvic development; behavioral traits, such as children’s play; social traits, such as development of social relationships; and cognitive traits, such as language and spatial abilities. He found that exposure to risks, such as environmental toxins or extreme social stress, will compromise these traits and more so for one sex or certain ages.

Alzheimer’s, toxins, anorexia

In the book, Geary uses this method to address questions about vulnerabilities. Among other topics, he discusses why women’s language competencies are more affected than men’s during the early stages of Alzheimer’s disease; why adolescent boys’ height but girls’ pelvic development is more compromised by poor nutrition; why boys’ play behavior is more easily compromised by prenatal exposure to toxins; and, why anorexia compromises girls’ and women’s ability to read social cues.

“This seemingly arbitrary mix of age, sex-, and species-specific vulnerabilities should be viewed with different filters for future research,” Geary says.

“By identifying and studying these traits, researchers should be able to determine specific impacts caused by disease, poor nutrition, social stressors, and exposure to man-made toxins and draw better conclusions for individuals based on age, sex-, and species-specific traits.”

Geary’s book, Evolution of Vulnerability: Implications for Sex Differences in Health and Development (Elsevier 2015), outlines the list of sex- and age-specific traits that he feels will be important for future study.

Source: University of Missouri

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